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Thermochimica Acta 563 (2013) 62– 66

Contents lists available at SciVerse ScienceDirect

Thermochimica Acta

jo ur nal home p age: www.elsev ier .com/ locate / tca

tandard molar enthalpies of formation for the two mixed alkali/alkaline earthetal borates of LiBaB9O15 and NaBaB9O15

ing Li, Rui-Bin Zhang, Zhi-Hong Liu ∗

ey Laboratory for Macromolecular Science of Shaanxi Province, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi’an 710062, PR China

a r t i c l e i n f o

rticle history:eceived 24 October 2012eceived in revised form 28 March 2013ccepted 3 April 2013vailable online 17 April 2013

a b s t r a c t

Two pure mixed alkali/alkaline earth metal borates with three-dimensional framework, LiBaB9O15 andNaBaB9O15, have been synthesized by high-temperature solid state reaction, and characterized by XRD,FT-IR, DTA–TG techniques and chemical analysis. The molar enthalpies of solution of LiBaB9O15 andNaBaB9O15 in 1 mol L−1 HCl(aq), and of LiCl·H2O(s)/NaCl(s) in [1 mol L−1 HCl + H3BO3 + Ba(OH)2·8H2O](aq)

eywords:ixed alkali/alkaline earth metal borates

haracterizationtandard molar enthalpy of formationolution calorimetry

have been determined by microcalorimeter at 298.15 K, respectively. From these data and with the incor-poration of the previously determined enthalpy of solution of H3BO3(s) in 1 mol L−1 HCl (aq), togetherwith the use of the standard molar enthalpies of formation for Ba(OH)2·8H2O(s), LiCl·H2O(s)/NaCl(s),H3BO3(s), HCl(aq) and H2O(l), the standard molar enthalpies of formation of −(6796.8 ± 7.3) kJ mol−1

for LiBaB9O15 and −(6829.9 ± 7.3) kJ mol−1 for NaBaB9O15 were obtained on the basis of the appropriatethermochemical cycles.

. Introduction

Boron has two kinds of unique coordination, BO3 and BO4,hich leads to the formation of a large variety of borates. There-

ore, borates can be a resource for functional materials. The studiesf alkali/alkaline earth metal borates have attracted considerablenterest because some of these borates can be as nonlinear opticalNLO) materials, such as CsLiB6O10, BaB2O4 (BBO) and Ba2Be2B2O7TBO) [1,2]. Some borates have three-dimensional framework, suchs LiBaB9O15 and NaBaB9O15 [3], in which both borates crystallizen the trigonal system with space group R3c and exhibit the samenionic group which is a three-dimensional framework built uprom B3O7 rings, with channels along the c axis in which the alkalinearth Ba2+ and the alkaline Li+/Na+ ions are located [3]. In addition,anoborate LiBaB9O15 was also obtained by Pushcharovsky et al.ith hydrothermal synthesis systems [4]. Han et al. reported flux

rowth, spectroscopic studies, and thermal properties (includinghe thermal expansion, specific heat, thermal diffusion coefficient,nd thermal conductivity) of single crystal of LiBaB9O15 [5,6]. How-ver, there are no reports on the standard molar enthalpies oformation for LiBaB9O15 and NaBaB9O15.

Thermodynamic properties play very important roles in sci-

ntific research and industrial applications. Until now, thetandard molar enthalpies of formation of many alkaline/alkaline-arth metal borates have been reported [7–20]. As part of the

∗ Corresponding author. Tel.: +86 29 81530805; fax: +86 29 81530727.E-mail address: liuzh@snnu.edu.cn (Z.-H. Liu).

040-6031/$ – see front matter © 2013 Elsevier B.V. All rights reserved.ttp://dx.doi.org/10.1016/j.tca.2013.04.009

© 2013 Elsevier B.V. All rights reserved.

continuing study of the thermochemistry of main group borates,this paper reports the determination of the standard molarenthalpies of formation of two mixed alkali/alkaline earth metalborates of LiBaB9O15 and NaBaB9O15 with three-dimensionalframework by using a heat conduction microcalorimeter.

2. Experimental

2.1. Chemicals

All reagents were used as obtained from commercial sourceswithout further purification. Table 1 summarizes relevant informa-tion on sample material purities. The water contents in Ba(OH)2 andLiCl hydrates are consistent with those of the molecular formula ofLiOH·H2O and Ba(OH)2·8H2O, respectively.

2.2. Synthesis and characterization of samples

Single crystals of LiBaB9O15 were synthesized from a mixture of0.168 g LiOH·H2O, 0.197 g BaCO3, 0.188 g Ga2O3 and 0.931 g H3BO3.This mixture was ground in an agate mortar and transferred toplatinum crucible, which was heated in a furnace at 900 ◦C for2 days, then cooled to 450 ◦C at a rate of 2.7 ◦C h−1, followed bycooling to room temperature at a rate of 20 ◦C h−1. The result-ing colorless crystals were collected, and washed with deionized

water and ethanol for three times, respectively. The single crystalsof NaBaB9O15 were synthesized referring to literature [3].

The obtained samples were characterized by X-ray powderdiffraction (Rigaku D/MAX-IIIC X-ray diffractometer with Cu K�1

N. Li et al. / Thermochimica Acta 563 (2013) 62– 66 63

Table 1Chemical sample used in this study.

Chemical name Source State Initial molefraction

LiCI·H2O Aladdin Solid ≥0.999BaCO3 Sinopharm Chemical

Reagent Co., Ltd.Solid ≥0.990

H3BO3 Aladdin Solid ≥0.998Ga2O3 Aladdin Solid ≥0.999Na2CO3 Sinopharm Chemical

Reagent Co., Ltd.Solid ≥0.998

t8rabar(Ncf[ire

2

hIvewale

�

L

N

ddtbHra

acoH

Tra

nsm

itta

nce

/%

Wavenumber/cm–1

1500 1200 900 600

50

55

60

65

70

75

80

85

90

95

100

1471.37

1389.54

1276.68

1107.39

906.06

850.63

780.10

737.77

689.08

643.14

583.36

518.76

1013.411245.79 994.25

a

Tra

nsm

itta

nce

/%

Wavenumber/ cm–1

1500 120 0 90 0 60 0

70

75

80

85

90

95

100

1385.60

1294.78

1092.42 990.24

956.18

920.12846.96

769.85

737.79685.78

649.14577.52

518.20

1016 .30

675 .141260.72

1456.96

b

Ba(OH)2·8H2O Jinjing Barium SaltChemical Co., Ltd.

Solid ≥0.9948

arget (� = 1.5406 A) scanning the 2� range with a speed of◦ min−1), FT-IR spectroscopy (recorded over the 400–4000 cm−1

egion on a Nicolet NEXUS 670 spectrometer with KBr pelletst room temperature), single crystal X-ray diffraction (recordedy a CrysAlisPro, Oxford Diffraction Ltd., Version 1.171.34.36 CCDutomatic diffractometer with graphite monochromatized Mo K�1adiation (� = 0.7093 A)), and thermogravimetric analysis (TGA)performed on a SDT Q600 simultaneous thermal analyzer under2 atmosphere with a heating rate of 10 ◦C min−1). The chemicalompositions of the samples were determined by EDTA titrationor Ba2+, by NaOH titration in the presence of mannitol for B2O321], and by ICP-AES elemental analysis (IRIS Advantage, charge-njection detector (CID), Thermo Scientific) for Li+ and Na+. Theelative standard uncertainty u(r) in the titration experiments wasstimated to be 0.2%.

.3. Calorimetric experiment

All the enthalpies of solution were measured with a RD496-2000eat conduction microcalorimeter (Mianyang CP Thermal Analysis

nstrument Co., Ltd., China), which has been described in detail pre-iously [20,22]. To check the performance of the calorimeter, thenthalpy of solution of KCl (mass fraction ≥ 0.9999) in deionizedater was determined to be (17.54 ± 0.10) kJ mol−1, which was in

greement with that of (17.524 ± 0.028) kJ mol−1 reported in theiterature [23]. This shows that the device used for measuring thenthalpy of solution in this work is reliable.

The thermochemical reactions designed for the derivation of thefHm

0 of LiBaB9O15 and NaBaB9O15 are expressed as follows:

iBaB9O15(s) + (HCl·54.561H2O) = LiCl·H2O(s)

+ Ba(OH)2·8H2O(s) + 9H3BO3(s) + 31.561H2O(l)

aBaB9O15(s) + (HCl·54.561H2O) = NaCl(s) + Ba(OH)2·8H2O(s)

+ 9H3BO3(s) + 32.561H2O(l)

The 1 mol dm−3 HCl(aq) solvent can dissolve all components ofesigned reactions, and its concentration, 1.0004 mol dm−3, wasetermined by titration with standard sodium carbonate. Withhe use of its density of 1019 kg m−3 (taken from chemical hand-ook), its concentration can also be expressed as the form ofCl·54.561H2O. Total time required for the complete dissolution

eaction was about 0.5 h. There were no solid residues observedfter the reactions in each calorimetric experiment.

The standard molar enthalpies of formation of LiBaB9O15

nd NaBaB9O15 could be obtained by solution calorimetries inombination with the standard molar enthalpies of formationf Ba(OH)2·8H2O(s), LiCl·H2O(s)/NaCl(s), H3BO3(s), HCl(aq) and2O(l).

Fig. 1. FT-IR spectra of samples: (a) LiBaB9O15 and (b) NaBaB9O15.

3. Results and discussion

3.1. Characterization of the synthetic samples

Single X-ray diffraction indicated that the samples of LiBaB9O15and NaBaB9O15 crystallized in the trigonal system with spacegroup R3CH, and the unit cell dimensions are a = b = 10.967(7) A,c = 17.060(14) A, � = 120◦ for LiBaB9O15 sample; a = b = 11.102(6) A,c = 17.400(9) A, � = 120◦ for NaBaB9O15 sample, which are con-sistent with the reported unit cell values in the literature [3],respectively.

As shown in Fig. 1, the IR spectrum of NaBaB9O15 sample is verysimilar to that of LiBaB9O15 sample, which indicates their similarstructures. Referring to the literature [5,24], we only assigned theabsorption bands of FT-IR spectrum for sample LiBaB9O15 as fol-lows: the bands at (1471, 1390 and 1277) cm−1 and 906 cm−1 mightbe asymmetric and symmetric stretching mode of B(3) O in thetriangular BO3 unit. The bands at (1107, 1013, and 994) cm−1 and(851 and 780) cm−1 were the asymmetrical and symmetric stretch-ing mode of B(4) O in the tetrahedral BO4 unit, respectively. Thebands at (738, 689, and 643) cm−1 are the out of plane bending of

B(3) O. The peaks at (583 and 519) cm−1 might be bending modesof B(3) O and B(4) O.

64 N. Li et al. / Thermochimica Acta 563 (2013) 62– 66

10 20 30 40 50 60 70

2θ / °

simulated

experi mental

toct

pw

((

Table 2Molar enthalpies of solution of LiBaB9O15(s) and NaBaB9O15(s) in 1 mol dm−3 HCl(aq)at 298.15 K.a

No. m (mg) �rH (mJ) �solHm (kJ mol−1)

LiBaB9O15

1 4.81 −2258.4 −226.102 4.60 −2161.8 −226.313 4.66 −2195.3 −226.864 4.51 −2117.2 −226.065 4.49 −2106.5 −225.92Mean −226.25 ± 0.33b

NaBaB9O15

1 4.65 −1574.4 −168.482 4.55 −1552.9 −169.833 4.72 −1601.5 −168.834 4.67 −1577.6 −168.105 4.57 −1546.5 −168.39Mean −168.73 ± 0.59b

Fig. 2. X-ray powder diffraction pattern of LiBaB9O13.

Figs. 2 and 3 show the powder XRD patterns of samples andhe simulated patterns on the basis of single crystal structuresf LiBaB9O15 and NaBaB9O15. The diffraction peaks on patternsorresponded well in position, respectively, which indicate the syn-hesized samples are pure.

The TG curves (Fig. 4) show that LiBaB9O15 and NaBaB9O15 sam-les have no weight loss from 30 ◦C to 800 ◦C, which are consistentith the two borates having no water or OH group.

The chemical analytical data of synthetic samples arefound/calcd, %), BaO (31.90/31.84), B2O3 (65.27/65.06), Li2O3.02/3.10) for LiBaB9O15 sample and BaO (30.97/30.81), B2O3

10 20 30 40 50

2θ / °

experi mental

simulated

Fig. 3. X-ray powder diffraction pattern of NaBaB9O13.

a In each experiment, 2.00 cm3 of HCl(aq) was used.b Uncertainty is twice the standard deviation of the mean.

(62.62/62.96), Na2O (6.29/6.23) for NaBaB9O15 sample. Moreover,the samples are free from Ga confirmed by elemental analysis. Thechemical analytical results are consistent with the theoretical val-ues.

All of above results indicate that the synthetic samples are pureand suitable for the calorimetric experiments.

3.2. Results of calorimetric experiments

The molar enthalpies of solution of LiBaB9O15 and NaBaB9O15in 1 mol L−1 HCl(aq) at 298.15 K are listed in Table 2. Themolar enthalpies of solution of LiCl·H2O(s) and NaCl(s) in 2 cm3

of [1 mol dm−3 HCl + H3BO3 + Ba(OH)2·8H2O](aq) at 298.15 K arelisted in Table 3, in which m is the mass of sample, �solHm is themolar enthalpy of solution of solute, and the uncertainty is esti-mated as twice the standard deviation of the mean.

Tables 4 and 5 give the results for the derivation of the standardmolar enthalpies of formation of LiBaB9O15 and NaBaB9O15. Themolar enthalpy of solution of H3BO3(s) of (21.83 ± 0.08) kJ mol−1

in 1 mol dm−3 HCl(aq) was taken from literature [17]. The molarenthalpy of solution of Ba(OH)2·8H2O(s) of −(55.42 ± 0.36) kJ mol−1

in [1 mol dm−3 HCl + H3BO3] (aq) was taken from literature [15].The standard molar enthalpy of formation of HCl(aq) and theenthalpy of dilution of HCl(aq) were calculated from the NBS tables

[25]. The standard molar enthalpies of formation of H3BO3(s)and H2O(l) were taken from the CODATA Key Values [26],namely −(1094.8 ± 0.8) kJ mol−1, and −(285.830 ± 0.040) kJ mol−1,

Table 3The molar enthalpies of LiCl·H2O(s) and NaCl(s) in [1 mol dm−3

HCl + H3BO3 + Ba(OH)2·8H2O](aq) at 298.15 K.a

No. m (mg) �rH (mJ) �solHm (kJ mol−1)

LiCl·H2O(s)1 1.06 88.8 5.062 1.02 83.8 4.963 1.39 115.7 5.034 1.11 92.0 5.015 1.24 103.3 5.03Mean 5.02 ± 0.08b

NaCl(s)1 0.78 182.4 13.672 0.65 152.1 13.683 0.74 172.9 13.654 0.54 125.8 13.615 0.59 144.8 14.34Mean 13.79 ± 0.28b

a In each experiment, 2.00 cm3 of HCl(aq) was used.b Uncertainty is estimated as twice the standard deviation of the mean.

N. Li et al. / Thermochimica Acta 563 (2013) 62– 66 65

Table 4The results for the derivation of �fHm

� (LiBaB9O15, 298.15 K).

No. Reaction �rHm� (kJ mol−1) Ref.

(1) LiBaB9O15(s) + 209.83(HCl·54.561H2O) = Li+(aq) + Ba2+(aq) + 3Cl−(aq) + 9H3BO3(aq) + 206.83(HCl·55.294H2O) −226.25 ± 0.33 This work(2) 208.83(HCl·54.712H2O) = 208.83(HCl·54.561H2O) + 31.561H2O(l) 0.63 ± 0.12 [25](3) 9H3BO3(aq) + 208.83(HCl·54.712H2O) = 9H3BO3(s) + 208.83(HCl·54.712H2O) −196.47 ± 0.72 [17](4) Ba2+(aq) + 2Cl−(aq) + 9H3BO3(aq) + 206.83(HCl·55.289H2O) = Ba(OH)2·8H2O(s) + 9H3BO3(aq) + 208.83(HCl·54.712H2O) 55.42 ± 0.36 [15](5) Li+(aq) + Ba2+(aq) + 3Cl−(aq) + 9H3BO3(aq) + 206.83(HCl·55.294H2O) = LiCl·H2O(s) + Ba2+(aq) + 2Cl−(aq) + 9H3BO3(aq)

+ 206.83(HCl·55.289H2O)−5.02 ± 0.08 This work

(6) 1/2H2(g) + 1/2Cl2(g) + 54.561H2O(l) = (HCl·54.561H2O) −165.45 ± 0.10 [25](7) Ba(OH)2·8H2O(s) = Ba(s) + 9H2(g) + 5O2(g) 3342.21 ± 0.24 [25](8) LiCl·H2O(s) = Li(s) + 1/2Cl2(g) + H2(g) + 1/2O2(g) 712.58 ± 0.32 [25](9) 9H3BO3(s) = 9B(s) + 27/2H2(g) + 27/2O2(g) 9853.2 ± 7.2 [26](10) 23H2(g) + 23/2O2(g) = 23H2O(l) −6574.09 ± 0.92 [26](11) LiBaB9O15(s) = Li(s) + Ba(s) + 9B(s) + 15/2O2(g) 6796.8 ± 7.3a,b

a Uncertainty of the combined reaction is estimated as the square root of the sum of the squares of uncertainty of each individual reaction.b eq11 = eq1 + eq2 + eq3 + eq4 + eq5 + eq6 + eq7 + eq8 + eq9 + eq10.

Table 5The results for the derivation of �fHm

e (NaBaB9O15, 298.15 K).

No. Reaction �rHme (kJ mol−1) Ref.

(1) NaBaB9O15(s) + 209.96(HCl·54.561H2O) = Na+(aq) + Ba2+(aq) + 3Cl−(aq) + 9H3BO3(aq) + 206.96(HCl·55.294H2O) −168.73 ± 0.59 This work(2) 208.96(HCl·54.717H2O) = 208.96(HCl·54.561H2O) + 32.561H2O(l) 0.65 ± 0.20 [25](3) 9H3BO3(aq) + 208.96(HCl·54.717H2O) = 9H3BO3(s) + 208.96(HCl·54.717H2O) −196.47 ± 0.72 [17](4) Ba2+(aq) + 2Cl−(aq) + 9H3BO3(aq) + 206.96(HCl·55.294H2O) = Ba(OH)2·8H2O(s) + 9H3BO3(aq)

+ 208.96(HCl·54.717H2O)55.42 ± 0.36 [15]

(5) Na+(aq) + Ba2+(aq) + 3Cl−(aq) + 9H3BO3(aq) + 206.96(HCl·55.294H2O) = NaCl(s) + Ba2+(aq) + 2Cl−(aq)+ 9H3BO3(aq) + 206.96(HCl·55.294H2O)

−13.79 ± 0.28 This work

(6) 1/2H2(g) + 1/2Cl2(g) + 54.561H2O(l) = (HCl 54.561H2O) −165.45 ± 0.10 [25](7) Ba(OH)2·8H2O(s) = Ba(s) + 9H2(g) + 5O2(g) 3342.21 ± 0.24 [25](8) NaCl(s) = Na(s) + 1/2Cl2(g) 411.15 ± 0.20 [25](9) 9H3BO3(s) = 9B(s) + 27/2H2(g) + 27/2O2(g) 9853.2 ± 7.2 [26](10) 22H2(g) + 11O2(g) = 22H2O(l) −6288.26 ± 0.88 [26](11) NaBaB9O15(s) = Na(s) + Ba(s) + 9B(s) + 15/2O2(g)

a Uncertainty of the combined reaction is estimated as the square root of the sum of thb eq11 = eq1 + eq2 + eq3 + eq4 + eq5 + eq6 + eq7 + eq8 + eq9 + eq10.

40

50

60

70

80

90

100

110

0 20 0 40 0 60 0 80 0

b

Wei

ght

/%

T /°C

T /°C

40

50

60

70

80

90

100

110

0 20 0 40 0 60 0 80 0

a

Wei

ght

/%

Fig. 4. TG curves of synthetic samples: (a) LiBaB9O15 and (b) NaBaB9O15.

6829.9 ± 7.3a,b

e squares of uncertainty of each individual reaction.

respectively. The standard molar enthalpies of formationof LiCl·H2O(s), NaCl(s) and Ba(OH)2·8H2O(s) can get fromthe NBS tables[25], which are −(712.58 ± 0.32) kJ mol−1,−(411.15 ± 0.20) kJ mol−1 and −(3342.21 ± 0.24) kJ mol−1,respectively.

From these data, the standard molar enthalpies of for-mation of LiBaB9O15 and NaBaB9O15 were calculated to be−(6796.8 ± 7.3) kJ mol−1 and −(6829.9 ± 7.3) kJ mol−1, respec-tively.

4. Conclusions

Through the appropriate thermochemical cycles, the standardmolar enthalpies of formation of LiBaB9O15 and NaBaB9O15 havebeen obtained from measured enthalpies of solution, together withthe standard molar enthalpies of formation of Ba(OH)2·8H2O(s),NaCl(s), LiCl·H2O(s), H3BO3(s), HCl(aq) and H2O(l).

Acknowledgment

Project supported by the National Natural Science Foundationof China (No. 21173143).

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6 imica A

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